The present invention relates to an injection molding apparatus and more particularly to an injection molding apparatus having means for providing better control of the temperature of the mold cavity.
Injection molding apparatus in general includes a pair of mold plates, at least one of which is movable toward and away from the other, each having a mold cavity in its surface which opposes the other member. Each of the mold cavities is usually of a size and shape corresponding to the size and shape of one half the article being molded. One of the mold members has a passage therethrough to its mold cavity through which the molding material is injected into the mold cavities. During the molding of an article in an injection molding apparatus, controlling the temperature of the mold numbers, both during heating and cooling, is an important part of the molding operation. During the injection of the molding material into the mold cavity, the temperature must be controlled to ensure complete filling of the mold cavity so as to obtain a molded article having the desired dimensions. This is particularly important when molding an article which is relatively large in diameter but also relatively thin. Also, good temperature control is desirable during the cooling of the molded article to maintain the desired dimensions of the article as a result of any contraction of the molding material and to prevent non-uniform stresses being formed in the article which could cause warping of the article. Therefore, it is desirable to have a molding apparatus which provides for control of the temperature of the apparatus during the various stages of the molding process.